Techniques for severing and sealing of metal tubes are well known in the art. See for example the U.S. Pat. No. 2,568,911 wherein a tube is sealed and then severed. In U.S. Pat. No. 2,851,580 a tube is welded closed using a pair of spaced apart electrodes which apply an electric current to seal the tube ends. U.S. Pat. Nos. 4,596,352, 4,619,397 and 4,736,881, see particularly the latter's FIG. 5, teach various methods and apparatuses for joining electric conductors using ultrasonic energy.
During the manufacture of a refrigerator, refrigerant must be forced into a compressor through a thin copper tube. In the prior art an ultrasonic welder was used to ultrasonically cut and seal the copper tube. In such equipment an anvil and a generally cylindrical tip are provided with the tip having a plurality of axially elongate tube welding surfaces distributed around the tip axis. The tip has cutting edges alongside the respective ultrasonic welding surfaces. The cutting edges cooperate with a shearing surface on the anvil to cut a tube after one side of the tube has been squeezed between opposing welding surfaces to seal the tube with an ultrasonic weld.
The ultrasonic welding process creates a tube temperature of about 550.degree. C., which is not a problem with a non-combustible refrigerant gas such as HFC. Hence, a copper tube would be simply welded and cut with an ultrasonic welder as described above and a seal would be made on the refrigerator's side. The severed tube leading to the supply of HFC gas would be left open and some gas permitted to escape. When other combustible refrigerant gases would be used, with ignition temperatures within the range of the temperatures developed during the ultrasonic welding step, ignition problem would arise.
It is an object of the present invention to provide an apparatus and method for cutting a tube and sealing both ends to prevent gas leakage from the cut tube. More specifically, it is an object of the invention to provide a safe apparatus and technique for cutting and welding copper tubes during filling with a combustible refrigerant.